This invention relates to an actuator for a magnetic disk devic, and more particularly to an actuator of the kind described above which is suitable for ensuring the stability of floating magnetic heads, improving the reliability of a signal recording and reproducing system and minimizing vibrations of the magnetic heads and magnetic disks.
An example of a prior art, magnetic disk device is shown in FIG. 5. Referring to FIG. 5, the prior art magnetic disk device includes a plurality of magnetic disks 6 mounted on a spindle 4 in a relation vertically spaced apart from each other by spacers, a spindle motor 9 rotating the magnetic disks 6 through a pulley 7 and a belt 8, a carriage 10 carrying magnetic head arms 1 supporting respective magnetic heads 3 (FIG. 4) thereon, a block 101 supporting the carriage 10 so as to be rotatable around a shaft, an actuator 11 positioning the magnetic heads 3, a base 12 supporting the actuator 11 thereon, cover 13 covering the parts described above to shield them from the exterior, and an annular filter 14 suspended from the cover 13 at a position directly above the center of rotation of the magnetic disks 6. The actuator 11 includes the carriage 10 and a voice coil motor 20 driving he actuator 11.
FIG. 4 shows the shape of the magnetic head arm 1. This magnetic head arm 1 is fixed to the carriage 10 by a head pin (not shown) extending through a hole A, and the magnetic head 3 is mounted through a gimbal 15 to a projection 91 formed at the front end of the magnetic head arm 1. The rotating movement of the carriage 10 causes a linear movement or a rocking movement of the magnetic head 3 above the recording surface of the associated magnetic disk 6. A signal is transmitted through a flexible printed circuit (FPC) 16 mounted on the surface of the magnetic head arm 1.
In such a magnetic disk device including magnetic head arms 1 each supporting a magnetic head 3 as described above, an improvement in the accuracy of head positioning becomes very important in view of the recent demand for an increased recording cpacity and an increased recording density. In order to meet the requirement for the improved accuracy of head positioning, various meand for preventing vibrations of the magnetic disks as well as vibrations of the magnetic heads have been proposed as described below.
(i) As an example, JP-A-59-84386 proposes a method of preventing vibrations of magnetic disks. According to the proposal, an internal shroud formed with many small perforations in its side walls surrounds magnetic disks to prevent turbulence of air flow. As another example, JP-A-56-137559 proposes a method of preventing vibrations of various parts of a magnetic disk device due to rotation of magnetic disks as well as vibrations of the magnetic disks. According to the proposal, a plurality of opposing sectoral spoilers communicating with the atmosphere are disposed above the recording surfaces of magnetic disks respectively to prevent the vbrations described above.
(ii) As a means for preventing vibrations of magnetic heads, JP-A-58-70459 proposes provision of baffle plates so as to prevent vibrations of gimbals supporting respective magnetic heads in a magnetic disk device. Also, in order to prevent vibrations of magnetic heads, JP-A-59-215072 proposes provision of a wind-shielding member in close proximity to the surface of a resilient support remote from the surface confronting a magnetic disk, thereby decreasing the amplitude of vibration of the resilient support and improving the effect of vibration damping.
However, even when prior art vibrations preventing or damping means as described above is applied, the prior art magnetic head arm 1 shown in FIG. 4, which is strongly affected by the stream and velocity of air flowing betwene the magnetic disks 6 rotating at a high speed, is swayed in the head positioning direction (the radial direction of the magnetic disks 6), and such a problem has arisen in which the magnetic head arm 1 together with the magnetic head gimbal 15 vibrates or resonates and the floating position of the magnetic head 3 is rendered unstable.
In order to ensure the stability of the floating position of the magnetic head 3, provision of spoilers fixedly disposed and extending linearly between the magnetic disks from the base has been proposed as described in (1) above. However, even when such spoilers are provided, difficulty has still been encountered in stably maintaining the floating position of the magnetic head 3 over the entire surface of the associated magnetic disk 6, since the condition with which the magnetic head 3 is exposed to wind, such as, the distance from the spoiler differs depending on the position of the magnetic head 3.
Due to the difficulty of stably maintaining the floating positin of the magnetic head 3, delicate displacement has occurred in the position of the magnetic head 3 carrying a servo head core for reading recorded informatin, especially, servo information, and a signal required for the head positioning control has been adversely affected.
Although attention has been directed to prevention of vibrations of the magnetic disks in the prior art, sufficient consideration has not been taken to prevent vibrations of the magnetic heads and magnetic head gimbals due to the direction and velocity or air flowing between the magnetic disks. Therefore, problems remain still in regard to the desired improvement in the head positioning accuracy and the required prevention of data destruction resulting from contact between a magnetic head and a magnetic disk due to the narrow spacing.